Nginx Strange rewrite/nginx issue

Hi guys,

I have tried everything and looking for any possible answer but I am lost .. please help me here.
This is my 2nd CentminMod install ... Currently using Standard setup + fastcgi_cache + ngx_pagespeed. (Everything is done following guides here and forum)
Site is working fine but I am randomly getting issue with rewrite. The browser will show 404 Not found error and the log will show

Code:

2014/12/06 11:17:45 [error] 15989#0: *22 "/home/nginx/domains/domain.com/public/2012/10/31/my-old-post-title/index.php" is not found (2: No such file or directory), client: x.x.x.x, server: domain.com, request: "GET /2012/10/31/my-old-post-title/ HTTP/1.1", host: "domain.com"

My permalink settings are

Code:

Custom Structure: http://domain.com/ %year%/%monthnum%/%day%/%postname%/

The site is running WordPress and forum but the issue is happening with just WP.

I may be going out of my mind but I think it's happening more when using Chrome ... Less with FireFox. And it will not happen on all posts. Sometime same blog post will work fine, and then give the above error.

---

Please help me, what to do, where to start looking?
Domain config file attached.

 

Tried to enable debug for error log.

Code:

2014/12/06 11:51:46 [notice] 16178#0: *180 "/wp-admin$" does not match "/2014/03/31/mobile-users-start-experiencing-3g/", client: x.x.x.x, server: domain.com, request: "GET /2014/03/31/mobile-users-start-experiencing-3g/?cf_action=sync_comments&post_id=49937 HTTP/1.1", host: "domain.com", referrer: "http://domain.com/2014/03/31/mobile-users-start-experiencing-3g/"
2014/12/06 11:51:46 [debug] 16178#0: *180 Passing on content handling for non-pagespeed resource 'http://domain.com/2014/03/31/mobile-users-start-experiencing-3g/?cf_action=sync_comments&post_id=49937'
2014/12/06 11:51:46 [error] 16178#0: *180 "/home/nginx/domains/domain.com/public/2014/03/31/mobile-users-start-experiencing-3g/index.php" is not found (2: No such file or directory), client: x.x.x.x, server: domain.com, request: "GET /2014/03/31/mobile-users-start-experiencing-3g/?cf_action=sync_comments&post_id=49937 HTTP/1.1", host: "domain.com", referrer: "http://domain.com/2014/03/31/mobile-users-start-experiencing-3g/"

I can't get why it's adding an extra "index.php" after URL.

 

I have two CentminMod installs and this is happening with just this one server. I m guessing it may be something with the theme (it's a custom one) or with some plugin. It's really a strange one.

And the kinda tricky odd part, when I am using Chrome I see 404 error page.
When I am using FireFox, page works fine. (even when there is log entry in error logs)

I am just clueless about it. I thought I will post here in case someone else experienced a similar issue.